Switched-mode power supply circuits such as synchronous buck converters provide power to a load through components such as capacitors, inductors, transformers, etc. and use switches that operate in an on or off state. Switched-mode power supply circuits dissipate very little power in either state and power conversion is accomplished with minimal power loss, thus yielding high efficiency. Switch-mode power supplies typically use semiconductor devices such as MOSFETs (Metal-Oxide-Semiconductor Field Effect Transistors). For example, a switched-mode power supply may include capacitors, an inductor, a MOSFET and a diode or alternatively a high-side MOSFET and a low-side MOSFET. Other component configurations are possible. In each case, components such as transistors, diodes and capacitors have associated parasitic elements that adversely affect the EMI (Electromagnetic Interference) or noise performance of the power supply circuit, thus limiting the switching frequency of the power supply.
For example, a switched-mode power supply circuit including a high-side MOSFET, low-side MOSFET and capacitor has a critical current loop that includes the drain-to-source current path of the high-side MOSFET, the drain-to-source current path of the low-side MOSFET and the capacitor current path from the drain of the high-side MOSFET to the source of the low-side MOSFET. The critical loop also includes the conductive traces or wires interconnecting the components. The parasitic inductance of the critical loop limits the switching frequency of the switched-mode power supply circuit. The parasitic loop inductance is a function of the loop area. Conventional switched-mode power supply circuits reduce the parasitic loop inductance by minimizing the area of the critical loop. Such solutions are highly dependent on the power supply package design and layout, and thus are effective for a particular type of package and layout. Redesign of the critical loop is needed each time the same switched-mode power supply circuit is included in a different type of package. Other conventional solutions involve a close arrangement of critical components. Further reduction in the parasitic loop inductance is desirable to increase the efficiency of switched-mode power supplies.